The present invention relates to a process for producing 1,5-diaminonaphthalene. 1,5-Diaminonaphthalene is a useful compound as a raw material for various synthetic resins. In particular, 1,5-naphthalene diisocyanate prepared from 1,5-Diaminonaphthalene is a useful compound as a monomer for polyurethanes having excellent physical properties.
Conventionally, 1,5-diaminonaphthalene is prepared by converting naphthalene into dinitronaphthalene by dinitration, and then by reducing the nitro groups thereof into amino groups. However, in the dinitration of naphthalene, a large amount of 1,8-dinitronaphthalene is generated as a by-product along with the desired 1,5-dinitronaphthalene. For example, in a method in which naphthalene is nitrated while removing water generated during reaction as an azeotropic mixture by distillation, whereas the yield of 1,5-dinitronaphthalene is 30%, the yield of 1,8-dinitronaphthalene is 65%. That is, the production amount of 1,8-dinitronaphthalene is twice as much as or more than that of 1,5-dinitronaphthalene (Japanese Unexamined Patent Application Publication No. 51-070757). 1,8-dinitronaphthalene is used as a raw material for dyestuffs, etc. Since the production of 1,5-dinitronaphthalene is linked with the production of 1,8-dinitronaphthalene, if the demand for 1,8-dinitronaphthalene is low, it becomes difficult to produce a necessary amount of 1,5-diaminonaphthalene.
In order to overcome such disadvantages, processes are disclosed in which a nitro imine and/or nitro enamine is prepared through two steps using ortho-nitrotoluene and acrylonitrile or the like as starting materials, and the nitro imine and/or nitro enamine is then aromatized and hydrogenated to produce 1,5-diaminonaphthalene (U.S. Patent Application Publication No. 2002/0103401 and PCT Publication No. WO02/090315). However, the nitro imine and nitro enamine, which are the intermediates in such processes, are relatively unstable compounds.
It is an object of the present invention to provide a novel process for industrially advantageously producing 1,5-diaminonaphthalene without formation of 1,8-diaminonaphthalene which is an isomeric by-product and not through a nitro imine and nitro enamine as intermediates.
As a result of thorough research on the object, the present inventors have found that it is possible to industrially advantageously produce 1,5-diaminonaphthalene from a naphthol compound which is obtained by the aromatization of 5-substituted-1-tetralone and have achieved the present invention. That is, the present invention includes the following Items.
(1) A process for producing 1,5-diaminonaphthalene including the steps of dehydrogenating 5-substituted-1-tetralone to produce a naphthol compound and then aminating the hydroxyl group of the naphthol compound.
(2) A process for producing 1,5-diaminonaphthalene according to Item (1), wherein the substituent in the 5-position of the 5-substituted-1-tetralone is a nitro group or an amino group.
(3) A process for producing 1,5-diaminonaphthalene according to Item (1), wherein 5-nitro-1-tetralone is dehydrogenated and reduced to produce 5-amino-1-naphthol, and then the 5-amino-1-naphthol is aminated.
(4) A process for producing 1,5-diaminonaphthalene according to Item (1), wherein 5-nitro-1-tetralone is dehydrogenated to produce 5-nitro-1-naphthol, the 1-naphthol compound is aminated to produce a 1-naphthylamine compound, and then the 1-naphthylamine compound is reduced.
(5) A process for producing 1,5-diaminonaphthalene according to Item (3), wherein 5-nitro-1-tetralone is dehydrogenated to produce 5-nitro-1-naphthol, the 1-naphthol compound is reduced to produce 5-amino-1-naphthol, and then the 5-amino-1-naphthol is aminated.
(6) A process for producing 1,5-diaminonaphthalene according to Item (3), wherein 5-nitro-1-tetralone is reduced to produce 5-amino-1-tetralone, the 1-tetralone compound is dehydrogenated to produce 5-amino-1-naphthol, and then the 5-amino-1-naphthol is aminated.